Nope, Paradox. They also make Europa Universalis 4, another major time sink.

Edit: You're right, Paradox is only the publisher in this case, not the developer as well.

Wikipedia says it's Paradox Development Studio, which is the design studio, where Paradox Interactive is the publisher, and both are under the same parent company. As far as I am aware, the 'clausewitz engine' used by these games isn't available to other developers.

Who are you seeing as the 'not-Paradox' developer for CK2?

Cities: Skylines. Wikipedia says it's made by Colossal Order, a Finnish company: http://en.wikipedia.org/wiki/Cities:_Skylines

EU4 and CK2 are made by PDS, part of Paradox Interactive, a Swedish company.

The confusion was because the thread is actually about Cities: Skylines. That's the game that's only distributed by Paradox, not also made by them, and the one I was confused about.

Sorry, I misread what the thread was about. Thanks for the clarification.